>From: DANMAS@aol.com
>
>The calipers started life at the factory apart, and were put together
>by semiskilled workers on an assembly line. What is there about them
>that keeps them from being separated and reassembled by us? As long as
>you use the correct "O" ring, and torque the bolts to the proper
>settings, I can't see what the problem is.
<SNIP>
>Of all the gazillion parts on the car,
>these are two of the least complicated parts there are.
Sorry about the diatribe coming:
All I've got to say is that when brakes fail, accidents happen.
In my opinion putting caliper halves together is indeed a very easy job AS
LONG AS YOU HAVE THE RIGHT TORQUE SETTINGS for the bolts.
Think of how much force is squeezing that brake rotor.
The opposite force is trying to push those halves of the caliper apart.
Remember that bolts are essentially like VERY stiff springs.
When you torque them down you are preloading or "stretching" them.
Just like other springs, if you stretch them too much, they can fail.
If you over torque them, then you are stretching them too close to their
failure point. Mash the brakes real hard and you can overload them. Once
one of them snaps, they all will.
My guess is that more than likely you weren't just sitting still in a
parking lot mashing the brakes either.
On the other hand it is important not to leave them too loose either.
When you stretch those bolts, you are clamping the two halves of the caliper
together.
If there isn't enough preload. . . or clamping force, it is possible to mash
the brakes real hard. . . then the force pushing the halves apart is greater
than the forces holding them together. The bolts don't necessarily fail . .
.they just "stretch" a little more.
Of course when they stretch, that means the two halves of the caliper are
getting a little farther apart. . . and the hydralic pressure on the brake
fluid is going to make it squirt out.
Once again. . . a catastrophy occurs.
There's a lot of engineering in there. . . we haven't even talked about
metal fatigue due to the thousands of thermal and tensile cycles put on
these bolts.
Yeah. . . putting a caliper back together is a pretty easy job.
But don't underestimate the importance of those torques.
It seems to me, the best way to get the right pre-load on these bolts would
be to measure their stretch with a micrometer. After all, you have access
to both sides of the bolt don't you?
Find a unmolested caliper, measure the length of the bolts both before and
after dissassembly. This will tell you how much the bolt "springs" were
stretched.
When you put the halves back together, don't worrry about torque at all. . .
just keep tightening them down until you get the same amount of stretch out
of your bolts.
Be careful about putting in replacement bolts.
If they are a higher grade. . . they are like stiffer springs.
Stretching them the same amount will make a much higher clamping force.
That may sound good. . . but it isn't really necessary.
Tink
Stepping off Soap Box, and putting on flak jacket.
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